Telephone system



June 5, E923.

ffy.

H. D. MaCPHERSON TELEPHONE SYSTEM Filed Dec. 51 1'91'9 4 Sheets-Sheet 1 l film jf-W 4 Ta LNH I WUM HHH

June 5, i923. 11,457,9112

H. D. MaCPHERSON TELEPHONE SYS TEM Filed Dec. 3l 1919 4 Sheets-Sheet 2 L uf l@ H. D. MECPHERSON TELEPHONE SYSTEM Filed Dec. 51 1919 4 Sheets-Sheet 5 I /ZS //7 by 1 www 'June 5, E923. 3,4519@ H. D. MacPHERSON TELEPHONE SYSTEM Filed Dec. ,31 1919 1 Sheets-Sheet 4 @Mr Mr wf /n Ver/fof.-

f/Mgh Mdc Phe/son by l Patented .lune 5, l923.

unirseN rares F Titi F HUGH DI MACPHERS'ON, OF'KSUMMITNEV JERSEY, ASSIGNORTO WESTERN'ELECTRIG COMPANY, INCORPOEALTED,` OliTNEW'" YORK, N. Y., A. CORPORATION'OF NEW YORK.'V

TritnPHoNnf'sYs'rEi/i.

Application'filed.December4 31, 1919. Serial No. 848,611.

To @ZZ w/i'om may concern Y Y Be it known that I, Hneiiil). liiiioPr'nnasoN, a. citizen .of the United. Statesi residing atSuminit iii the: count otUnion ,State et Ehew Jersey, lia-yev invented'certain new anduseiul Improvement-s iiiTeleplioiie Systems, oitwhicli the following is a iull, clear?, coiicise, and exact description.

This invention.l relates to telephone l'sys- 10 tenis and more particularly tov such-systems in which the signals for a plurality otitiiinls-r lines extending; between widely separated stations. are controlled over a single signah iiioijpath eoniinon to suelitrufnlr lines.;

Ansysteins ot' thisz character it has been proposed to employ at oppositeeends of the signaling patlnsignal sending means tor transmitting over the signaling` pathv codesignals individualto'tlie different tr'unlelines- 2e and determinedtby the `trunk line in signaling; condition. 1

It isL the ob)l ect` of t-liis :invention Ltoprovide improved means for determining and setting up the different code signals `to be transmit ted by the signal sending means. for sendingV the signals :is soon. asset-- upland tor preventing the. simultaneous setting up and transmittingfof twocodesignals in the saine direction.

The means provided by the present invention for attaining, this object willy be more readily understoodibyi reference to the ac companying drawings in which Figs.-A lv to.

3 is located at an oi'iice Z. A telephone line- (ir-is also shown terminating ina jack 117' at olice-Z. A- single trunk line '2' terminating in a jack 2l at otlice- X and-a' plug 10G atx oliice Y is shown but in raetice man f suoli.

lines would.v be associatedrwith-'a single sigeria-lingr path common to a groupv of lines..1 One toll switching trunk. H terminatingin a j acl:-y 101 .andy aiplug 129 `for extending connections from. oficeeY to line is shown, but itis to be understood thatl any suitable vnumber might be used.` nly that end of a cord circuit F which cooperatesv with the trunl lines L is shown, as the other end of this cord circuit may be of any design suitablefor cooperating with subscribe-rs or local trunk lines terminating in tliefoilice l Below the horizontal dotted liney inlFig. l are shown sets of relays J, K and lvl forA determining the code signal to be set up for each individual line belonging to a group.

One such set of i'elaysis provided.tor,` each`r line in a group, but as their circuits are identical with the exception of' tlieeonductors to which theright-hand contacts of the relays lvl are tied, onlyv the sets individual.

to lines L1, L2, L'andfLl have been shown.

li roni each set ot relays .three conductors.v il', B and@ extendto` apparatus*individual to the line which controls these relays, only those extending, to lineL2 beingsho-Wn in full, since the other conduetorsii, Bland C,

extend to corresponding points inxtheir re'- speetive lines. v

ThelJ, K and-M` relays together;l withthe relays shown in Fig. 2 constitute the impulse storing and sending equipment designated SE.. In F ig. e is; sho-wn theimpulse receiving. equipment RE', .comprising impulse re.-A ceiving relays at the leftof tliedraiwing,and vpyramid linel selecting' relaysfatthe right ot thedrawing, The contactsof relayslQO to 197 areeconneetedto.conductors-D individ-l ual to the `lines of thegroup, but' as-they all lead to corresponding pointsfn their respective lineequipinent, onlyi conductor D2 individual to linel. is shown in'ifull;V impulseA receiving' equipment is pioifidedat oiliee X..

but as it isidentical with that at otliee Y, it has been indicated by the dotted rec'- tangle RE iii the lower right-.hand corner. of Fig. 2. Similarly impulse sending equip-- nient identical with SE atoliice X ispro-` vided at olice. Y and is indieatedby the dotted rectangle SE in the lower lett-hand corner of, liligt.y Lilie apparatus atvotlices- X and Y is numbered alike, without primes at oiiice X, with primes. at oilice` Y. In

order thatsignalsniay be. sent in opposite directionssiinultaneeiisly duplex equipmentcomprising differentially wound polarized relays 40 and 40 and'. artificial lines AL', is connected vto the ends ofthe common signaling conductor P at ofiicesh and Y res aectively.

be Vunderstood from a consideration ol' ,the

lo- Ommeczoa cord cercati If teeth. mmh

I rllhe Voperatorat.the oliice X; desiring to' lt is to be noted that slow operating; and releasing relays employedare conventionally illustrated as suoli by arrows intersectingg, the armatures or said relays and` pointing in the. direction. ino-Which said armatures arey slow to move.

It is'belieVe-d that the invention will now operation'oi? the system which is kas follows Zine L2.

establish a connectionv with the telephone i line circuit Gr terminatin` atolrce Z, connection With which line must be established f through oliceY, .communicates in `the usual Aao l relay 22, and the normal Contact manner With the operator at oliice Y an order Wirecircuit (not shown). The operator at oiiice X upon ascertaining trom th'e operator at oliice Y that the trunk line circuit L2 shallbe used in completing the connection inserts the calling plug,- lor a link circuit F at olhce X into t)ach 2l of the (trunk line L2. Relay 22 thereupon operates over a circuitextending yfrom 'battery through lampV 23, the sleeve contacts of plug 20 and jack 2l and the Winding` of relay-22 toground. However, the resistance of the Windingot relay 22 is sullicient to prevent the/.lighting or' lamp 23. A circuit is the-reupon established r4from vbattery]throughl re-.

sistance 37, the Winding and normal. contact of relay 24,'the alternate contact voll ol relay 28 v to ground. Relay 24 operates due tothe current `flo-Wing through this circuit and locks over a circuit extending from battery through resist-ance 37' and the'winding` and tact-of relay J 2, th'e left-hanzd normal con-r tactof relay J2, and Winding thereof, con-v ductor A2, the right-hand lnormal contact ol?` ymiddle alternate contact oit relay 24 to ground. A circuit for relay is `also yclosed thel `right' lhand [alternate contact marginal,

relay 24. ,A circuit-is also formedl `from tact of relay J1, the rightliand normal ron- 1 relay y0, the. alternate contact of ,relay 22,

and the normal cont-act of relay 28 to ground. 'Relay J2 operates and locks over a circuit extending from battery through the left-ha`nd Yalternate contact andA ivinding of relayiJ 2, conductor A2, the right-hand'non Nmalcontact of relay 30, the alternate r`conv tact of relayl 22 and the normal contact oit relay 428 to ground. They opening of the right-hand normal contact or' relay J 2 inter# rupts they continuity of the battery supply 4circuit 'for operating the J relays associated with the succeeding lines of the-system.

'lhe` closure of the right-hand alternate contact of relay J2 operates'relay K2over a circuit extending from battery through the Winding.' of relay K2, the right-hand alternate contact of relay J 2, the middle normal contacts, in series,"of the intervening relays betweenthe relay J 2 and the relay J 2,1' tothe right-hand normal contact of relay 122 to ground'. `The opening of the middle nor Amal contact of relay'fdr 2 interrupts the continuity of the 'conductorleading to they preceding K relays. Relay M2 thereupon operates over a circuit extending from battery ythrough the Winding of' relayl 2, the middl'e contact oft relay K2, and the normal contact of relay` 38 to ground.` The closure ot' the lett-hand contact or' relay M2 Yin operatf ing prepares a 'circuit for relay k50 and the closure ot the vright-hand alternate contact yof relay l. 2completes a circuit extending 'from battery through the Winding of relayl 41, thewinding or relay 45, and theright hand alternate contact ot relay M2 to ground. lTh'e'closure of the right-hand con-` tact otrelay 41 causes the operation of relay' 43v over a circuit extending from battery through the Winding or relay v43,- the righthand contact of relay4l, the 'upper normal contact of relay 52 andythe upper' normal contactof relay 5l to ground. Y The opening of the normal contactof relay` 45y Vremo-ves the ground connection from` the conductor leading to' the polar relay 40, included in the common signaling path P and the closure of theright-hand alternate contact of relay 43, connects such common signaling path` to an armature of relay 45.. Thejclosure of the letthand alternate contact ot" relay 43 completes a circuit lfor relay 42, which extends from battery through the [Winding of relay 42, the left-hand Contact of relay 41, and the left-hand Contact of relay 43, to ground. llelay 47 thereupon oppath l), for a predetermined length of time,

through the normal contact of relay/47, the left-handl alternate contact of relay 45, and' the right-hand alternate contactl of relay 43.

kRelay 47 in vopening its normal contact dis-` ables this circuit and completesa circuit which extends from batter-y through the` Winding ofrel'ay`46, thel upper alternate contact of relay 47, the righthand alternate contact of relay 45, and the contact of relay 42 to ground. rllhe closure oic the left-hand alternate contactofv relay 46 completes-a circuit ior relay y58, extending `from battery through the Winding of relay58,the righthandnormal contacter relay 55, and the left-hand alternate contact of relay46,to

ground. However, afterA the operation vot :iA-exagerar.

*contacty of relayl 58,v thev letl'tfehandA normal.

contact of. relay 55, `the rightfhand: alternate Contact of relay 46, the lower alternate-contact of relay; 47,.the left-hand alternate contact of relay.` 45, andI they right-hand altere nate contact` of relay 43, thustransmitting an impulse of reversed polarity;A Relay. 56 then operates over alcircuit extending from battery through the.winding` of: relay. 56,.

thel upper alternate contact ot relay; 5.8 the right-:hand normal Contactv ofirelay'55, .an-d',

the. left-hand alternate Contact of relay'46, to ground.l Relayv 68 thereupon operates over a circuit extendingy yfrom battery through the winding of relay 68, the.` righthandnormal contact@ of'V relay 65,y the lett;- hand alternate contactA of relay '56, to ground. However, subsequent to@ the opera tion of relay- 56, and prior tothe-complete operationot' relay 68,.the negative terminalof the 120 volt.s sourceof` current is; again connected to the common vsignaling path P,

the circuit for such currentbeingl traceable from the negativetermmal ot such source.

through the normalpcontact of relay, 68the lett-hand normal Contact, of relay 65, the right-hand alternate contact ot re-lay: 56., the lower alternate contactfotrelay 58j, the lette hand normal contact; of relay; 55, the=right hand alternate Contact' of relay 46, the lower alternate cont-'act ofi: relay 47 theg-lett-.hand f alternate Contact offrelay 45, and-` the righthand alternate contact ofZrela-y 43; temporary connectionof-the lQOyolt source of current. transmits. another impulse off negative polarity over-the common signaling path P. Relay 66 then.,operates-through the upper alternatefcontacta of: relay '68, the

right-,hand normal contact of relayV and the lett hand alternate; contact ot relay'56l Lto ground. Relay 78 then'v operates over a circuit extending from battery.. through zthe winding of relay Y78, the right-handrnormal contact otrelay 75, and the lett-hand` alternate contact of relay 66-to ground; Howe ever, as before, during-the interval between the operation ot relay 66 andtheacomplete operation of relay 78, the negative terminal of thek 120 volt source of: current is again` connected to the common signaling path P,

t-he circuit for such current being traceable from the negative terminal'ot such source= through the normal' contact of: relay 78, theY lett-hand normal contact of relay 7 5, thev right-hand alternate Contact otrela'y 66, the lower alternate Contact otfrelay` 68,ftlne-leiit-l hand normalcontactot relay.v 65, the-'righthand alternate Contact ot'relay 56, the lower alternate Contact of relay 58, the lett-hand normal contact ot relay. 5.5, .thef right-.hand alternate contact of relay 46,- they lower.

This` alternate contactot.; relay 47, the left-hand .alternate contact otrelay 45, and the rightthen operates over alcircuit extending from battery through the winding ot relay 88, the rightehandnormal Contact of relay 85, and the left-hand alternate Contact ot relay 76 to ground. As inthe previous cases, between the timel relay 76 operates and relay 88 completes its operation, the negative terminal o" the l2() yvolt source ot current is temporarily connected with the common signalinggpathfl?, the ycircuit in this instance being traceable from the negative terminal ofthe 120 volt source ot current through the normal contact of relay 88, the left-hand normal contact of' relay 85, the right-hand alternate Contact of relay 76, the lower alternate contact oit relay 78, the left-hand normal Contact of relay 75, the right-hand alternate` contact ot' relay 66, the longer alternate Contact ot relay 68, the left-hand ternate contact of relay 47, the lett-hand alternate Contact ofrelay 45, and the rightL hand alternate contact of relay 48. operations tran-smity another impulse of negative polarity over the common signaling,v pat-h l?. Relay 86 now operates in the same manner as vrelays 46, 56, 66 and 76 over an obvious circuit; Relay 52 then `operates over aA circuit extending from battery through the winding ot" relay 52, the right hand normal Contact 01"' relay 50, and the left-hand alternate Contact ot relay 86 to ground. v

As in the previous eases, however, the negative terminal of the 120 volt source of current is again temporarily connected with the common signaling path l?, the circuit in this instance being traced trom the negative terminal ot' the 120 Volt source ot current through the lower normal contact ot' relay Thesel ythe right-hand alternate contact ot'relay 46, lthe lower alternate contact of relayv 47',

the lett-hand alternate contact of relay45, andA the vright-hand :alternate contactv ot' relay 43. Relay 43 releases upon the fopening of the upper normal contact ot relay 252,

thus causing ythe release of relay 12"whi'cl1 in'turn removes the ground connection trom' the `circuit including'the windinglotrelay 47 land the latter relay in releasing in response to-this operationeauses the release f reiaysfae, 56, e6, 6s, 66,781,76, 86,86 ai` sequence, and the release of relay disconects the signal initiating relays from association with the common signaling path?" and-restores the normal ground connection thereto. The closure of the "upper alternate n contact otl relay 52 completes a circuit tor while the' circuit for relay 39'ex`tends fromv battery through the winding ot relay 39,

the upper alternate contact of' relay 52, and

the upper normal contact ofrelay 51to ground. Relayy 38operates over thecircuit traced therefor prior to the operation 'otr Arelay 39, wliichis slightly slow iii-opening its contact, and locks over a circuit -estabf lished from battery through the winding and left-hand alternate Contact of relay 38 to the yright-hand contact ot relay K2 where 'it joins the circuit previously traced Jfor the latter relay. A circuit isy also completed from battery through the winding and the left-hand normal contactof relay 30, leadl B2, .the lett-hand alternate contact yot relay K2, and the right-hand alternate contact of relay 38 toy ground. Relay 24 is short-circuited and released by the ground on con-v ductor B2, 'but again energizes and-locks overthe circuits previously traced therefor when said ground is removed. It will-be noted that`A while conductor B2 remains grounded, relay 24y upon operating, is immediately shunted and released so that such relay is intermittently operated until. the ground is removed from such conductor. Howeventhis' condition is only momentary while the impulse is being 'transmitted and produces no material eilect upon the system, since relay22 remains operated. Relay responds tothe current flowing 'through the circuit'y and in operating, locks'over a circuit extending from battery through the winding and lett-hand alternate contact ot relay 30,' the alternate contact of relay 22 andthe normal contact of relay l28, to ground. vThe opening of the right-hand normal contact of relay 3() causes the release oli-'relay J2y which in turn releases relay Ktand'relay M? insequence, the release oi' relay M2 releasing relays 45 and 41. The

release oi relay J2y opensV the locking circuit otrelay 38 to deenergize this relay 'and thereby remove ground from lthe conduc-v tor B2 whereuponr relay 24 again `energizesand locks. Relay 52j releases 'upon the 're-f7" lease ot 'relay 86 so-thaty all apparatus'iu connection with the signal restoring and signal sending equipment at oflice'X is re-Uy stored to vnormal except relays 22, 24 and 3 0 which remain in an operated condition. 75

I The first signal transmitted over the'com- Y mon signaling pathlJ in response to the op!v eration ot' relay 4,causes relay 40 at oiiice Yito close'its upper contact, thereby completing a circuit from batterythro-ugh the 80 normal contact ot relayv .134", the right-hand normalA Contact and left-hand winding ot relay 132, the right-hand normal contact of' relay 131 and the upper contactof relay 40 to ground. Relay 132 operates and re-l85 vlay 131 thenvoperates over a circuit extending from battery# through the normal eontact of `relay 134.','the windings oit relay 1 32,v in series, the left-hand alternate contact ot such relay and the'winding otrelay`131" to 90'* ground. 1n operating relay 132 opens' its normal contact, removing the normal shortcircuit eXisting around the right-hand wind-` ing of such relay, thus-reducing the current flow thro-ugh the windings ot such relays to a predetermined amountfthus preventing injurious'ei'tects which might result from a continued liiow'of the original operating vcurrent. Relays 190, to 197,rinclusive, thereupon operate over a vcircuit extending from lo battery through the windings of such relays`- in series and the right-handalternate contact ot relay 132 to ground. The second impulse received over the commonsignaling.path l being oi the opposite ypolarity causesrelay 40to close its lowercontact whereupon relay operates overa circuit,"extending from battery through the normal contact ot relay 134, the let-handcontac't and righthand` winding ot relay 140, the vleft-hand 110 normal contact 'of relay 141, the lett-handA alternate Contact of relay 131, and the lower contact ot relay 40 to ground. The opening o'f the normal contact ot relay`140, as in w the case of relay 132, removes the normal`11`5 short circuit from thelet-'hand winding of such relay and the closure ot' the `right-hand contact of relay 140 causes the operation of relay 141 over a' circuit extending from thecircuit for relay 140', through the right- 120 hand contact thereof 'and the winding of relay 141 to ground. The next impulse received over the common 'signaling path causes relay 40 to close its lowercontact whereupon relay 150 voperates over a cir- 125 cuit extending from-battery through the con'- tactot lrelay 134', thel left-hand contactandthe right-hand winding of relay the lett-handnormal contact ot rela 151', the" klett-hand alternate contact otrelay 141,the` 1,80

leit-'ha'nd alternate "contactof relay 131 and `thelower contact ot'relay 40 to ground. "Rellay 1501inoperating removes'the short circuit existingarouml'its lett-hand winding :and causes'the operation of relay 151 in a 'manner similar to that described `for relays 1.410 and 141. The .succeeding imiulse transmitted, being of the same 'polar-ity,

causes relay 40 to again close its lower con- -tact,fthereli y causing-thc operation ot Arelay 160 over a circuit extending vfrom battery :.throughthe contact of relay 13'r4,the leit- 'hand contact and right-hand winding otrelay 160,`the left-handfnormal contact ot' re- :lay V161',thelett-hand alternate contacts of -relays'151, 1`41.,"and 131l in series, andthe lower contact otrelay 40 to ground. Asin circuit `existing aroundits left-hand winding The impulse ltransmi'tted over th' polarity,c`auses relay L10 'tol'again close its lower contachwhereupon relay 170 oper- `vat'e's over a 'circuit extending from battery through the contact ot relay '1341,the left- `hand contact 'and 'right-hand winding` ofre- Slay 170, the left-'hand normal contactoif relay 1171. the iri'ghtlhand alternate contacts ofrclays 161, 15.1, 1411, and 131 'and "the lower contacts of relay 14:0 to ground. VAs in `the case of relay 140 and 1111, relay 170 in operating 'removes Ythe vnormal short circuit existing aroundits fl'efthand winding and causes the operationfofrelay 171. The next impulse being of a similar vpolarity again causes relay 40" `to close its -lower contact whereupon relay 130 operates over a circuit extending from:batteryfthroughthe contact of relay 134, the normal contact and Vright-hand winding of relay 180', the leithand alternate contacts of relays 171, 161, 151",'111, and 131 infseries, andthe lower contacto'f relay '40 to ground. As in the previous instances, relay 130, iii-operating, Aremoves the normal short circuit existing around its left-hand winding and causes the operation of relay 131.

The closure et the left-'hand alternate contact of .relay 130 also completes a circuit extending` from `the positive terminal of battery through the contact and winding of relay 1'33,fthe left-hand alternate contact of relay 1'30, thefnormal contact of relay 153i', the 'lower normal Contact of relay 163, the lowernormal Contact of relay 17e', the lower normal y.contact of relay 1S6,and -the lower alternate cionta'ctof relay 197, where it connects Vwith receiving fconductor B2 'and extendsthrough the left-hand winding of relay `1:16 to ground. Relay 116 is vthereby operated and 'locks over a circuitextending from battery through its right-hand alteri distributing yopening of the right-hand alternate contact nate "contact yand rightih'and Winding "to ground. In closing its aleifthand calternate contact, relay 116 causes the lighting of guard lamp 138 over a'circuit extending from battery through the lamp v138, the nor mal contact of relay 103, and the lett-hand alternate y contact of relay 116 to ground,A as

.vellas causes the operation of transferre- Ilay lliover an obvious circuit to connect conductor D2 with the Vrigl'itlhand 'winding 'of relay 114 through the contact-of 'relay i115,butdue'to'the `cessation of the impulse,

no ei'liect isproduced upo'nrelay 51114. Re-

lay 133 in #operating removes the normal short circuit Aexisting around 'resistance A136 to reduce the currentfllowing through lthe signal conductor to fa safe value 'fora continued low, and relay 181 1n operating,

causes the operation oit Yslow-`o'perating 'relay 134, thereby Iremoving the b`atte1y-`convnection Afrom the circuits overwhic'h rela-ys 1313132', 11i-031411', 150, iai/,1160311613 '1.70, i171', 180and 131 arefheldfenergized,

thereby releasing 'such relays and bytherelease of relay 1S1"causing thelrele'ase ofrelays 133 and 134e to restore the limpulseapparatus "to normal.y The of relay 132" releases relays 190 to 1197":inelusive, thereby restoring the 'pyramid selecting relays tol normal.

'Uomtccz'on of 'toll switching trunk :H wt/L Zinc G.

At the time the operator at office Y-desiglnaties the ltrunk line ywith Iwhich operator at oiiice X vconnect-ed the cord Lcircuit F, the operator at office Y also communicates with the oflice'Z over an order wire circuit (not shown), advising the operator thereat the i number of the line with which connection fis desired, whereupon the operator at the otlicc Z designates the toll switching trunk circuit over which the connection should be 'established from'oiice Y to oiice Z. .Assuming that the toll switching Atrunl; .circuit kH `isith'e one designated, the operatoriat'office Zth'ereupon inserts the plug 129 of vthe 'trunk cir cuit H into the jaclr 117 of fthe Ilineicircuit G. Sleeve relay 125 and vcut-olf 'relay '1:13 operate over a circuit extending from battery through the windingiof relay l125,;the sleeve contacts of plug 129 and j'acl. 117,' and the winding relay 118,'to ground. rPhe operatioi'i-o'f the cut-oill relay 113 disconnects the line relay 119 from the line conductors'i'n the usual manner. The .operation "o' "the sleeve relay 4125 ca uses the lii olrtin'g of supervisory lamp 124 over a circuit extending from battery through the lamp 124, the lower alternate contact-.of relay 125, the 'resistance '123, and the normal contact o'frel'ay 121 to ground,

Y is thereupon completed extending from bat- Uonnectz'on of trunk Zine circuit L2 with toll switching trunk circuit H.

plug 100 and jack 101, to'ground. The closure of the contact of relay 102 causes the operation of relay 103 over a circuit extending from-.battery through the Winding of yrelay, 103, and the contact of relay 102, to

ground. rlhe closure of the upper alternate contact of relay -103 establishes the continuity of the tip conductor of the trunk line circuit L2, which conductor'is normally discontinuous for the purpose of making the usual busy test. The opening of the lower normal contact ofrelayf103 causes-the eX- tinguishment of guard lamp 138. Acircuit tery through the left-hand Winding of relay 121, the left-hand normal contact of relay 122, the tip contacts of jack 101 and' plug 100, theupper alternate contact of relay 103, the upper normal contact of relay 104, kthe Winding of relay 105, the middle normalcontact of relay k104, the ring con-.

tacts oli' plug 100 and jack 101, the righthand normal contact of relay 122, andthe right-hand Winding of relay 121 to ground. Supervisory relays 105 and 121 are operated due to this circuit.l Theoperation of supervisory relay 121 extinguishes supervisory lamp 124 and the operation of relay 105 vcauses the operation of relay 106 over a circuit 'extending from battery through the Winding of relay 106, and the alternate contact of relay 105 to ground. Relay 108 also operates over a circuit extending from battery through resistance 143, the Winding and normal contact of relay 108, the contact of relay 107, and the alternate Contact of relay 105 to ground. Although a circuit is also completed at this time for relay '107, such relay does not operate due to its slow operating nature, until after relay 108 has operated. Relay 108 in operating locks over 'Y a circuit extending from battery` through resistance 143, the Winding and right-hand alternate Contact o1 relay 108. to ground..

The closure of the left-hand alternate contact of relay 108 causes the operation of relay109 over a circuit eXtending'rom battery through resistance 110, the Winding l and normal contact of relay-109 and the lefthand alternate contact of relay 108` to ground. Relay 109 locks over a circuit eX- tending from battery through resistance 110 and the Winding and left-hand alternate 'contact of relay 109 to ground. The closure of the left-hand alternate Contact of relay 108 also connects ground with conductor A2 leading -to the relay .lf2 of the sending equipment SEv aty oiiice Y tofcause the series of operations ofthe vrelays of such sendingl equipment correspondingto those# previously described, for therelayso'f the sending equipment a't office X caused by the grounding of conductor A2 following the insertion of the plug 20 of the link circuit F into the jack 21 thereat. ,These impulses cor-t respond in arrangement and characterk to those previously'transmitted and select the i line L2 at the ofiice Xin the saine manner that line L2 was selected at the office Y. The impulses are received by the receiving equipment RE at oiiice X which equipment corresponds with the receiving equipment at oiiiceY and the last impulse upon being transmitted over the receiving conductorl)2 at oflicefX causes the operationV of relay 32,1'

parallel `relation'o'f resistance V54A and the .a

Winding of relay 22, theamount ofcurrent ovving through this circuit is sufficient to cause the lighting of the lamp 23 lto indicate to theoperator at olice X lthat the plug 1 00 has been inserted in the jack 101. -I-lowever, insuficient current is diverted from relay 22 to cause its release at this time.' Upon 'the grounding of thelead B? of the sending equipment SE at office Y occurringfin the sequence described for the grounding of lead B2 at oiiice X, relay 108 releases'due to the shunting of the Winding thereofl by the resistance 143. Thus ground is removed from the lead A2 of the sending equipment SE in a mannerk `similar to that described in connection With the relay 30 at oiiice X. The sending equipment SE thereupon is restored to its normal condition and is capable of being used in connection with any other line controlled thereby. f 1

They operator' at oce X actua/,tes the ringing key. The operator at office X, upon observing the lighted condition of the supervisory `lamp 23, actuates ringing key associated with line circuit F, thereby causing the operation of the ringing response relay 28 over a circuit established from the source of alternating current, through the lower alternate contact of'ringingv key 60, through the ring contacts of plug 20 and jack 21, the Winding of relay 28, condenser 29, the tip `contacts 'of jack 21 and plug 20 and the upper alternate contact of ringing key 60y to ground.

veo'

v-zrfrfsaara The closure of the Aalternate `contact of ringing response relay 28 y'causes'thefoperation oit' relays 26 fand 27.over-obvious circuits, the operation of relay 27 causing fthe short-circuiting of the windings of the I'epeating coilfthereby eitectually preventing the transmission lot ringing current over the conductors of line L2=to-the distant lstation. The opening'o'f the :normal contact of relay 26 interrupts the locking circuit lof relay 30fto relcaset'he saine but kvrelay 24 remains operatedfover'its locking circuit. Relay 30 in openingits right'hand alternate contact interrupts Athe circuit ytorysupervisory lamp 23 to extinguish this`^lanip,to inform the operator that the Ysignal sending vapparatus is functioning. l/Vhen the signal 'has vbeen sent relay 30 is operated as beforeto again complete the shunt of relay'22 through resistance 54; to 'light supervisory lamp 23.

Relay 26, in operating, connects ground 'to lead A? through the lalternate contact vot relay A26, Vthe valternate contact ot-relay 22, and the right-hand normal contact ot relay 30. Thereupon the AYsaine series 'of operations follow` als-described in connectionwith the operation of relay 24 in connection with the initiationotthe call. ARelays J2, K2, M2 and the other associated relays vfunction in exactly the same y'manner as previously described. to transmitover the common signaling path P a similar setV ot impulses which -are received by the relay lOand 'cause the signal distributing and pyramid `selecting relays at otlce Y to again select the -conductor D2 associated Iwith lthe line L2 at otlice Y. Following theselecti'on o1 theiline,

`the last impulse ot'theseries is received over the line conductor 'DZ and fiows through the i contact of relay -115 and right-hand winding of relay 114 to groundcausing the operation ot relay 114. Although this impulse also flows through the left-hand AWinding of relay 116, no effect is produced thereby :since it produces magnetic uX in the same direction as that producedby the current flowing through the locking circuit of relay 116. Relay 1111 thereupon locks over a circuit extending trom battery through the left- 'hand winding and right-hand alternate contact ot relay 1111. and the -lower normal contact of relay 101 tov ground. Slow release relay 113 thereupon operates over -an obvious circuit causingthe subsequent operation of relay 111 over an obvious circuit and ot relay 104 over a circut extending from battery through the winding Yof Vrelay '104 and the contact 'ot relay 113 toground. 'The closure of the contact of relay 1'11 mgaintains relays 10,6 `and 107 in an operated 'condition -independently of supervisory relay 105 which -releases upon the-opening of the upper andiniddle normal contacts of relay 10-1, The opening ofthe lower Ln'orm'a'lfconing its operatedfperiod,relay 104 completes a `temporary circuit extending from the source of alternating current through the lower alternate contact of relay 1011, the ring contacts of plug 100 and 'jack 101, the winding of relay 120, condenser 128, the tip contacts of jack 101 and plug 100, the up- -pe'r alternate contact of relay 103 and the upper alternate vContact of relay 104 to ground. Relay 120 in operating, causes the `operation of relays V122 and ringing relay 127 vover 1a circuit extending from battery through the left-hand winding ot relay 122,'tl1e winding of relay 127, and the contact ofrelay '120 to ground. Relay 122 in operating disconnects relay 121 from the talking conductors of the toll switching trunk H during the-time that ringing cur- -rent is connected -therewith andby the vclosure ot its left-hand :alternate ycontact prior to 'the lopening of its 'left-hand normal contact maintains relay 121 operated over a circuit lfrom battery through the left-hand winding of relay 121 and the left-hand alternate cont-act of relay 122 to ground. The operation of relay 127 causes the operation ot the subscribers bell'at the station G over acircuit extending'from the source vof alternating current through fthe upper alternate contact of relay 127, the ring contacts lot' plug 129 and'jack 117, the winding of the -if'ibrating bell at the station G, the tip contacts of jack 117 and plug 129, the upper alternate Contact ot relay 125, and the lower alternate contact 'of relay 127 to ground. Upon the deenergization of relay 104, the `ringing current ris disconnected from the conductors of line L2 leading to the toll switching'trunk H causing the release of relays 120, 127 and 122 in sequence, the releasefof the llatter krelay reconnecting relay 121 to its original operating circuit so that relay 121 is maintained operated and relay 105 reoperates. Theclosure of the Contact of relay 105 maintains relays 106 and 107 Voperated after the complete release of relay 111.

Operator at .X restores rin-ging key.

Upon t-he restoration of the ringing' key :to normal` relay 28 decne-rgizes causing the release ot'lslow yrelease relay 26 and ot relay/'27, the latter relay renioring the shortcircuits established. around the windings of the repeating coil. llelay 26 closes its normal-contact. tomaintain a locking circuit for relay'BO prior to the interruption of the circuit for this Irelayvthrough the Aalternate contact fof relay 26.

The reccirer of zf/z-e station on, telephone Zine t? s :remorel fromy the sterfte/rhode.

The subscriber at the station on the telephone line .Gin responding tnt-he operation ofthe call `ibe'll th'er'eat, removes vthe V*receiver circuit, therefor, being traced `from battery through the leit-l'iandwinding ot relay 1.22, the contact ot relay 126, the right-hand Wiiidingv oit relay 122, andthe alternate co-ntact o1c rela,7 121 to ground. Relay 122 in operating disconnects relay 121 trom the circuit.includingthe supervisory relay 105 of the line .circuit L4 but jrelay 121 is maintained energized dueto the completion of a circuit extending from battery through the left-hand Winding of relay 121 and the alter-v nate contact of relay 122 tol ground. Relay 105 is deenergized due tothe opening-of its operating circuit. Relay 11.1 beingreleased, the opening oit the `alternate contact oit relay interrupts the circuit ot relays 106 and 107 to deenergize these relays. The release of relay 107 completes a circuitffrom battery through resistanceV 143, the Winding andnor- 'mal contact o'l relay 108, the normal contact of relay 107 ,the normal contact of relay 105, the right-hand alternate contact of relay 1.09, the normall contact oit relay 106 4and the .Windingof rela-y `144 to ground. Relay 108 operates over this circuit and vlocks over a 'circuit extending from batterythrough resistance 143, the Winding and right-hand alternate contact 0i relay .-108 to ground. Relays 106 andV 144 also operate over al circuit extending trom battery through the Winding otrelay 106, the norma-l contact of relay 1.05,

theright-hand alternate contact of' relay 109, the normal contact of relay `106 and-the Winding ot relay 144 to ground. vInlinediately upon the operation of relay 106, relays 144 and 106 lock over a circuit extending trom battery through the Winding' of relay 106,/ thenormal contact of relay 105, the right-hand 109, the alternate contact of lrelay 106, the right-hand alternate Contact' and Winding of relay 1.44 tov ground. Relay 107 being 'slow in operating does not operate prior to the operation of relay 108, but then operates.

over a circuit from battery through the Winding of relay 107, the normal contact of relay 105 and thence in parallel with the eircuit for relay 106 through the lWinding of relay 144 to ground. y The closure of the middle contact out relay 144 connects ground to conductor Cl2 leading to the sending equipment SE', and the closure 4oli-the' lett-hand alternate contact of lrelay alternate yContact 'of relay 108A connects ground Withthe conductor 1121eading to the sending equipment SE-, as inthe previous cases. The grounding of the conductor` A causes the series of operations ofthe sending equipment apparatus, as previously olescribed, to transmit; the i samey .arrangement of selecting impulses as'previously@titansn mitted-upon. the insertion of the plug 100 into i the jack 101, but due tothe :tact 'that-.the

conductor C2 is, grounded, pole vchanging relay 50 is operatedso'that the operation of relay 86, in connection with :the last selecting impulse, 51 instead of relay 52'-, as in the previous instances, and as a consequence, the positive terminal of the; volt source of currentlis temporarily coneeted to the signaling path through the vlower normal contact .of relay A51 and relay 50', instead olf the negative terminal l of the 120 volt source oli current being connected thereto through the lower normal. Contact ofgrelay v52 and the lett-'hand normal Contact of relay 50,. as in the previous instances. As a `resulto'f this change in-the connection for the last impulse, the 'current is reversed, so that upon being received at ollice X the uppercontact otrelay 40 is` closecl,-Whieh causes the operation of relay 182 of the receivingequipment .RE-by the means ofcurrent. flo-Wing through the nor- .mal eontaetof relay 134, the normal Contact and left-hand Winding of relay 182, instead of through the normal 'Contact of relay 134,

causes-theoperation'oi relayy the left-hand alternate contactl ot` the normal Contact and. right-hand Winding of'relay 180, as in the previous cases. kThus in closing therighthand alternate contact of relay 182, a cireuit-iscompleted whereby negative current is sent out over v receiving conductor D2, through the contact and Winding of relay 185, instead of positive current being sent out through the contact and Winding of v`relay 133. rllhe last impulse, therefore, traversing the conductor D2, flows lio through the right-hand Winding of relay 32 in such ya direction as to diiierentializesuch relay and cause it to release its armatures.

kThe opening of thepright-hand. Contact of relay 32 causes the release 'of slow-releasing relay 33, the release ot relays 35 fand 36 `in s equence. 4The opening of the left-hand alternate` contactv of relay 32 disables the branch circuit` including the resistance 54, so that such resistance-is no longer in parallel relationwvith the winding of relay 22, and as a consequen ce,lamp 23 is extinguished, thus notifying the operator at4 office X that the subscriber at the station on the line G has answered. As in the previous instances, upon sto'ringthe impulses in the.

sending equipment SE., the conductor- BZ- is grounded, thereby causing the release of relays. llOSand 109 by shunt/ing 'the windings which inv turn causes of such relays through the associated resistances 1113 and 110 respectively. The release of relay 103 removes the ground connection from the conductor A32, and the release of relay 109 opens the locking circuit. oit relays 106, 107 and 144, thereby allowing such relays to return to normal. Receiver of t/Le station on tetcpfzone Zine G' s replaced upon the switch/rooie.

rt the conclusion of the conversation the subscriber at the station ot the telephone line G- restores the receiver to the switchhoolr, whereupon supervisory relay 126 defy energizes, opening the circuit of and releasing relay 122. The closure of the normal contacts oi.E relay 122 restores relay 121 to its normal association with the talking conclue tors oit the toll switching trunk l-l, whereupon relay 105 is operated, over thecircuit previously traced, in series with relay 121. ln response to the operation of relay 105, relay 108 is operated and locked as previously describedinconnection with the signal transmitted froml oilice Y to office X upon the insertion of the plug 100 in the jack 101. As in the preceding instance also, the grounding of the conductor A'2 by the closure of the left-hand alternate contact of relay 108 initiates the series of operations of the sending equipment SE to transmit the same series of selecting and signaling impulses, as in the former case. These impulses upon being received for the signaling path P cause the operation of relay l10 to transfer such impulses into the receiving equipment RE at oilice X to select Vthe signaling conductor D2 of the line L2, and to transmit thereover an impulse of vcurrent of positive polarity causing the operation and locking of relay .32, as in the previous instance. Resistance 54 is again included in parallel with the winding of relay 22 to reduce the resistance in series with the supervisory lamp v23 causing the same to be illuminated. Relay 33 also operates upon the closure of the right-hand alternate contact of relay 32 and relay 32 locks over the circuit including its middle alternate contact and lefthand winding, as in the previous instance. Relays 35 and 36 also operate in sequence following the operation of relay and the signaling' conductor D2 is connected to the left-hand winding of relay 34 through the lcictdiand alternate contact of relay 33.

Operator at oyjce X disconnects @ont circuit -F from trunk Zinc circuit L2.

The operator at office X, upon observing the continued illumination of supervisory lamp 23, removes plug 20 from the jack 21 causing the release of relay 22. Relay 30 is released by the opening of the alternate contact of relay 22 and an operating circuit for relays J2 and 31 is thereupon completed from grounded battery through the righthand normal contact ci relay J1, the righthand normal contact of relay J2, the lefthand normal contact and windingk of' said relay conductor A2,' the left-hand normal contact of relay 30, the normal contact of relay 22, the lett-hand alternate contact of relay 2&1 and the windingof relay 31 ,to ground. The energization of relay J 2 in this circuit. as in the previous instances, causes 'the operation vof relays K2and M2. The operation of relay M2, however, performs .an additional function atk this time which consists in completing a circuit extending from battery through the winding o1 relay 50, the left-hand contact of relay M2, the conductor C2 and the contact of relay 31 to ground.- In response to the operation of the relay M2 and the relays controlled thereby, the same series of selecting impulses is impressed upon the signaling path l), as in the case of the initiation of the call, but due to the operation of relay 50, the operation of relay 86 causesthe operation ,of relay 51 insteadot relay 5 2, so that the last or signaling impulse is transmitted -from the positive terminal of ythe 120 volt source of current through the lower normal contact of relay 51 and the left-hand alternate Contact of relay 5.0, instead of from the negative terminal .of the volt source of current through the lower i normal contact of relay 52 and the left-hand normal contact of relay 50. W'hen relay 38 operates in response to the operation of relay 51, it connects ground over the path previously traced to conductor B2, shunting relay 24 through resistance 37. Relay 24 in opening its left-hand alternate Contact opens the circuit :for relays 31 and J2, and relay J2 in deenergizing restores the impulse sending and storing equipment at office X in the manner previously described.

The selecting impulses being received at office Y cause the relay 40' to initiate the same series of operations of the signal im.- pulse vdistributing and pyramid-selecting relays atoiiice Y as were described in connection with the initiation of the call, whereby the signaling conductor D'2 leading .to the trunk line L2 is selected. However, due to the reversed polarity of the signaling impulse following these selecting impulses, relay 182' operates instead of 180', the circuit for the former relay being traceable from battery through the normal contact of relay 134', the normal contact and left-hand winding of relay 132', the right-hand alternate contacts of relays 171', 161', 151', 141' and 131' in series and the upper Contact vof relay 40' to ground. As in the previously described case, the opening' of the normal contact ot relay 182 removes the normal shortcircuit existing around the right-hand winding of relay 182' to reduce the current flowl ing through the circuit, and vthe closure of the left-hand alternate contact ofrelay 182y causes the operation of relay l181 over a circuit extending vfrom battery through the normal contact of relay 134', the windings Vof relay 182 in series, the left-'hand alter nate contact thereof, and thewinding of relay 181 to ground. The closure of the contact of relay 181 causes the operation of A relay 134,``as vin the otherpcase, to remove the batteryfrom the various signal impulse receiving relays, allowingV them to returnto normal. However, during the operation of relay 182 an impulse D? through the contact and winding of relay 135f, the resistance 137 being included -in circuit with the winding of relay 135 upon its operation for the purposes of protection, as previously outlined in connection withrelay 133. This signaling impulse being of thek opposite polarity with respect to the impulse causing the operation of relay .116, causes relay 116 to become diiierential- 'ized 'when it flows through the left-hand winding of such relay. Upon the release of relay7 116 ini response to this diierentializing.

action, lamp 138 is lighted overa circuit eX` tending from battery through the lamp 138,

., the lower alternate contact ofrelay 103 and switch'ng Relay 115 is also released due to the o energized due to the removal of. the receiver at station G from its switchhook by the answering of the called subscriber, and the consequent series of impulses acts, as in that case to send an impulse of negativepolarity through the right-hand winding of relay 32` Vat oiiice XL This impulse vcauses ymagnetic `flux in the opposite direction to that caused by the locking winding of relay 32,

so thatthis relay is deenergized. Relay 32 in opening itsVright-handk Contact deenergizes relay 33, and consequentlyl relays 35 and 36,`so that all the equipment at office X is;'now`restoredftoy normal. The operation of relay 38 at the end of this series of impulses grounds conductor B? to shunt relays108 and l109 through resistances 143 and 110 respectively, and relay 109 in opening v` itsv right-hand contact deenergizes relays 107 106 and 144 so'that all the apparatus at office Y is now completely restored. The release ofsupe'rvisory relay 121, due to theremoval of plug 100 from jack 101causes the illumination of supervisory lamp 124 over a cilu of negative polarity isconnected with the signaling 'conductor cuit extending from `'battery through the lamp 124, the loweralternate contact or reA lay 125, the resistance 123 and the normal contact` or relay 121 to ground.-r The operator at otiice Z,-up"on observing the lighted condi-k tion of the lamp 124, removes plug 129 from the jack 117 whereuponl all apparatus associated with the line circuit (ir and the toll switching trunk H. returns to normal. y

Subscriber et .station on telephone Zin/@VG recalls the operator at office X.

Should the subscriber at the station on the telephone line Gr, after answering a call when connection is established between the toll cord circuit F and the telephone line Gr by way of the trunk line L2 and the toll switching trunk HL, wish to signal the `ropera-tor atoffice X, this be accomplishedby rapidly opening and'closing the switch-V hook contacts at the station on' the telephone line G. The first opening of the-switchhook contact would cause the operation of relay of the connected trunl; line L2 which will cause the same series of 'selecting and signaling impulses to be transmitted'from o'liice Y,as in the case when the calledv subscriber at the station'on line Gr *replacedl his receiver on its switchhoolr at the terminationfoic the conversation.'y The signaling impulsewhich is received by the conductor D2 causes the operationv of relay 32, which in turn causes the operation;l of relays 33, 35 and 36, as' the previous case, thereby completing .a shunted path through resistance 54 around the winding or relay 22, as in the previous case, and causing the illumination of supervisory lamp. 23. j The first closureoi1 the switchhook contacts would cause the deenergization of relay 105, but as relay 106 yis energized at this time no circuit is completed for relay 108 and no impulses are sent out. vBefore relay 1067 which is slow to release, closes its normal contact to complete a circuit for relays 108 and 144, thesubscriber has again opened his switchhook contacts to again complete energizing circuits forrelays 108, 106k and 107, so that relayk 106 remains energized throughout the rapid open-v yings and closures of the switchhook contacts,

and an impulse of positive polarity is trans'- mitted over conductor D2 each time the contacts are opened. The second of these impulses is transmitted through the leit-han`d contact of relay and the left-hand wind'- ing of relay 34 to ground, to operate relay 34. A temporary locking circuit is also comico pleted for relay 34 from battery throughthe right-hand winding and left-hand alternateV contact of this relay and the contact o'li` relay 36 to groundgi. circuit is thereupon conirupter '59 and the'right-'hand alternate con'- tact of relay 34, instead of the right-hand normal contact ofsuch relay in series with .pleted rwhich includes thegroundedinter#v the resistance 54. Therefore, during the continued operation of relay 34, the supervisory lamp 23 will be ilashed at a definite rate by the rotation of the interrupter 59. HOW- ever, the opening of the left-hand normal contact of relay 34 releases relay 33, which in turn removes the signaling conductor D2 from its association with the left-hand Wind ing of relay 34C and causes the sequential release of relays 35 and 36. the release of the latter relay causing the release of relay 34, thereby removing the interrupter from its relation with the circuit including the lamp 23. It, however, relay 34- is released before the subscriber ceases operating his switchhool., relay 33 is again operated and thereafter relays 34, 35 and 36 are operated in the mannervdescribed. Thus, provided the openings and closings of the sivitchhook contacts at 4the station G are suiliciently rapid, the relays 3&1. and 32 Will be maintained in an operated condition so that the interrupter is continued in association with the circuit including the lamp 23. However, upon the sivitchliook remaining in either position for a sutdcient period, the' relays at olice X will function to produce either a steady lighting of the lamp 23 or a permanent extinguishment thereof, as the case might be.

The operation described above with reference to the establishment of a connection with the telephone line G for the trunk line L2, and the breaking-down oi such a connection, are characteristic oi those taking place in establishing and breaking-down a connection over any one of the trunk lines to which the signaling path l? is common. The only essential diiierences in operation, so far as the establishment of the connections over the different trunk lines is concerned, lies in the fact that different code signals are employed for the different trunk line circuits, and diiierent sets of relays J, K and will be operated, and the signal impulse storing` relays, such as relays 45, 55, 65, 75 and 85 will be operated in different combinations to determine the polarity and arrangement of the signaling impulses to be transmitted over the signaling path through the sending relays associated With the storing relays. These different combinations of impulses upon being received at the distant otlice are distributed and cause the locking of different locking relays ot the distributingl system, which in turn control the pyramid-selecting relays to connect the signalreceivin conductors of the various lines With the signal transmitting circuit associated with the signaling relays. l/Vhile signal receiving conductors D have been shown for only 32 lines, it is obvious that any number oi lines might be associated with a common signaling path by the use of additional relays such as 85, Without departing from the spirit of the invention.

What is claimed is:

l. In a telephone system, the combination with a plurality of trunk lines and a signaling path common thereto, ci' a train of krelays common thereto for transmitting over the signaling path code signals individual to the dierent trunk lines, a set of normally inert relays individual to each line for determining the code of signals ior its associated line, and means controlled by a change in condition of any one of the trunk lines for operating its set of relays.

2. In a tele-phone system, the combination with a plurality of trunlr lines and a signaling path common thereto, of a train of rela-ys common thereto for transmitting over the signaling pathr code signals individual to the different trunk lines, a set of normally inert relays individual to each line for determining the .code of signals for its associated line, means controlled by any change in vcondition of any one of the trunk lines forr operating its set of relays, and means for preventing the operation of a .set of relays individual to a second line While said set of relays are in operated. condition.

3. ln a telephone system, the combination With a plurality of trunk lines and a signaling path common thereto, of a train of relays common thereto, for transmitting over the signaling path signals comprising a denite number of current impulses of positive or negative polarity, a set of relays individual to each trunk line for operating said train of relays and for controlling the polarity oi a certain number of the impulses in each signal, a control relay for controlling the polarity of the remaining impulses of the signal, means responsive to any change in condition on any one of said trunk lines for operating` its set of relays, and means responsive to certain particular changes of condition on any one of said trunk lines for operating said control relay.

l. ln a telephone system, the combination with a plurality of trunk lines and a signaling path common thereto, of a train of relays common thereto, for transmitting over the signaling path signals comprising a delinite number of current impulses of positive or negative polarity, a set of relays individual to each trunk line for operating said train of relays and for controlling the p0- larity of a certain number of the impulses in each signal, a control relay for controlling the polarity oi the remaining impulses of the signal, means responsive to any change in condition on any one of said trunk lines for operating its set of relays, means responsive to certain particular changes of condition on any one of said trunk lines for operating said control relay, and a relay individual to the impulse receiving end of said trunk line operated in response to said signal when said remaining impulses are current of one polarity connectedto a lnor- 5. In a telephone system, a. train of relays, a signaling path, means for selectively operating said train 0i relays, a source of inal contact of each relay of said train, a source oily current or opposite polarity connected to an alternate contactk of each relay of said train, means responsive to the opera-r tion of said selective operating means for extending said signaling` path to one of said contacts of the first relay of'said train, a pair lof relays and-a third relay individual to each vrelay of said train, means for operating,- one or the other ol'l said pairyof relays in accordance with the energized or inert condition ot its'train relay to disconnect said signaling path from the source of current and iso-operate said third relay to eX- tend said signaling path to one of said sources of current through a contact of the next relay of thetrain, said third relay causing the operation of the relays assorelays for extending Said signaling paththrough a contact of one relay oi!- said train to one of said sources of current, and a set of relays individual to each relay of said train operated in response to said yextension oi' saidsignaling` path to disconnect` said path from said source of current andtoextend it through a contact of another yrelay of said train toeither of said sources of current dependinf upon theeondition of the last mentioned relay of the train.

ln Witnesswvhereo, I hereunto subscribe my name this 29th day of December-A.` D., 1919. f

HUGH n. inornnnsoN.` f 

